Filtern
Dokumenttyp
Schlagworte
- Additive manufacturing (13)
- Laser powder bed fusion (8)
- Residual stress (7)
- Additive Manufacturing (6)
- AlSi10Mg alloy (4)
- Computed tomography (4)
- Residual Stress (4)
- X-ray refraction (4)
- AlSi10Mg (3)
- EBSD analysis (3)
- Electron backscatter diffraction (EBSD) (3)
- Fatigue crack growth (3)
- In situ heating (3)
- Laser Powder Bed Fusion (3)
- Neutron diffraction (3)
- Residual stress analysis (3)
- Creep (2)
- Diffraction (2)
- Diffraction elastic constants (2)
- Digital image correlation (DIC) (2)
- Electron backscatter diffraction (2)
- Fatigue crack propagation (2)
- Heat treatment (2)
- IN718 (2)
- In-situ heating up to 1400°C (2)
- Inconel 718 (2)
- LPBF (2)
- Microcracking (2)
- Neutron Diffraction (2)
- Refractory materials (2)
- Residual stress state (2)
- Residual stresses (2)
- Sintering (2)
- Synchrotron X-Ray Refraction (2)
- Synchrotron refraction radiography (2)
- Synchrotron µCT and refraction radiography (2)
- Texture (2)
- Thermally induced porosity (2)
- A357-T6 cast aluminum alloy (1)
- A357-T6 casting (1)
- AGIL (1)
- AISI 316L (1)
- AM IN718 (1)
- AM IN718 alloy (1)
- Al-3.85%Mg alloy (1)
- Aluminium alloys (1)
- Aluminum alloy (1)
- Analyzer-based imaging (1)
- As-built LPBF IN718 alloy (1)
- Bench braking sequence (1)
- Bragg-edge neutron 2D imaging (BENI) (1)
- Braking load history (1)
- Bulk properties ageing (1)
- Cellular structures (1)
- Ceramics (1)
- Ceria (1)
- Components influence (1)
- Composite (1)
- Composites (1)
- Compression testing (1)
- Compressive test (1)
- Computed Tomography (1)
- Crack initiation period (1)
- Cracks (1)
- Crystal plasticity finite element modeling (CPFEM) (1)
- Crystallographic descriptor (1)
- Crystallographic texture control (1)
- Cyclic R-curve (1)
- DIC assisted compression (1)
- Damage characterization (1)
- Damage tolerance (1)
- Defects (1)
- Denoising filter (1)
- Diffraction methods (1)
- Diffraction peak width (1)
- Diffraction-elastic constants (1)
- Diffusion (1)
- Digital image correlation (1)
- Dislocation-climb-controlled creep (1)
- Dislocations (1)
- Distortion (1)
- Distortion upon baseplate removal (1)
- Effect of scanning strategies (1)
- Electron microscopy (1)
- Energy dispersive X Ray diffraction (1)
- Ernel average misorientation (KAM) (1)
- Evolution of bulk properties (1)
- Fatigue performance (1)
- Fractals (1)
- Fractographic observations (1)
- Friction braking (1)
- Geometric descriptor (1)
- Graphite induced hysteresis (1)
- Hystersis (1)
- IN718 PBF-LB/M (1)
- Imaging (1)
- In situ testing (1)
- In-situ (1)
- In-situ heat treatment (1)
- Inconel (1)
- Interfaces (1)
- Interphase residual stress (1)
- Keramik (1)
- Kernel average misorientation (1)
- L-PBF (1)
- L-PBF IN718 material (1)
- Laboratory XµCT (1)
- Laboratory energy-dispersive X-ray diffraction (EDXRD) (1)
- Laminated metal composite (1)
- Laminated metallic composites (1)
- Large Scale Facilities (1)
- Laser Beam Melting (1)
- Laser Powder Bed Melting (1)
- Laser beam melting (1)
- Laser powder bed fusion (LPBF) (1)
- Laser-based additive manufacturing (1)
- Lattice Structure (1)
- Load history (1)
- Macroscopic stress (1)
- Mechanical behavior (1)
- Metal additive manufacturing (MAM) (1)
- Metal matrix composite (1)
- Metallic matrix pad (1)
- Microstructural evolution (1)
- Microstructure (1)
- Microstructure and texture (1)
- Monoclinic to tetragonal transformation (1)
- Near-surface X-ray diffraction (1)
- Neutron and X-ray diffraction (1)
- Neutrons diffraction (1)
- Nickel-based superalloys (1)
- Nonlinear stress-strain curve (1)
- Online Process Monitoring (1)
- PBFLB/M AlSi10Mg alloy (1)
- Phase transformation (1)
- Plasticity (1)
- Pore size (1)
- Porosity growth (1)
- Post processing heat treatment (1)
- Powder analysis (1)
- Powder metallurgy (1)
- Power law and power-law breakdown (1)
- Power-law breakdown (1)
- Propagation modes (1)
- Pure aluminium (1)
- Qquantification and segmentation (1)
- Re-entrant surface feature (1)
- Refractory (1)
- Refractory zirconia (1)
- Residual stress in AM (1)
- Residual stress measurements (1)
- Röntgen-Refraktion (1)
- SIF evaluation (1)
- Scan strategies (1)
- Scan strategy influence (1)
- Scanning electron microscopy (1)
- Scanning electron microscopy (SEM) (1)
- Selective laser melted materials (1)
- Semi-metallic brake-pad material (1)
- Semi-metallic friction material (1)
- Semi-metallic sintered material (1)
- Si network disintegration (1)
- Stainless Steel (1)
- Statistical image analysis (1)
- Statistically relevant volumes (1)
- Steady-state creep (1)
- Stiffness (1)
- Strain-free lattice references (1)
- Strain-free lattice spacing (1)
- Stress balance (1)
- Stress balance condition (1)
- Stress-relief heat-treatments (1)
- Surface roughness analysis (1)
- Synchrotron Energy Dispersive Diffraction (1)
- Synchrotron X-ray computed tomography (1)
- Synchrotron X-ray diffraction (1)
- Synchrotron X-ray diffraction (SXRD) (1)
- Synchrotron X-ray refraction (1)
- Synchrotron X-ray refraction radiography (1)
- Synchrotron computed tomography (1)
- Synchrotron refraction (1)
- Synchrotron tomography (1)
- Tensile testing (1)
- Thermally induced microcracking (1)
- Thermally induced porosity (TIP) (1)
- Thermography (1)
- Ti-6Al-4V (1)
- Tiatanium (1)
- Torsional fatigue (1)
- Torsional in situ fatigue testing (1)
- Toughening mechanism (1)
- Toughening mechanisms (1)
- Uniaxial compression tests (1)
- Verbundwerkstoffe (1)
- Wear resistance (1)
- X-Ray refraction (1)
- X-ray Computed Tomography (1)
- X-ray Diffraction (1)
- X-ray Refaction radiography (1)
- X-ray analysis (1)
- X-ray and Neutron Diffraction (1)
- X-ray and neutron diffraction (1)
- X-ray synchrotron tomography (1)
- Zirconia (1)
- pure aluminum (1)
- subgrain (1)
Organisationseinheit der BAM
- 8 Zerstörungsfreie Prüfung (57)
- 8.5 Röntgenbildgebung (57)
- 9 Komponentensicherheit (15)
- 9.4 Integrität von Schweißverbindungen (14)
- 5 Werkstofftechnik (5)
- 5.1 Mikrostruktur Design und Degradation (3)
- 5.2 Metallische Hochtemperaturwerkstoffe (2)
- 8.0 Abteilungsleitung und andere (2)
- 9.0 Abteilungsleitung und andere (2)
- 9.6 Additive Fertigung metallischer Komponenten (2)
Eingeladener Vortrag
- nein (10)
Layer-by-layer additive manufacturing (AM) by means of laser-powder bed Fusion (L-PBF) offers many prospects regarding the design of lattice structures used, for example, in gas turbines. However, defects such as bulk porosity, Surface roughness, and re-entrant features are exacerbated in nonvertical structures, such as tilted struts. The characterization and quantification of these kinds of
defects are essential for the correct estimation of fracture and fatigue properties.
Herein, cylindrical struts fabricated by L-PBF are investigated by means of X-ray computed tomography (XCT), with the aim of casting light on the dependence of the three kinds of defects (bulk porosity, surface roughness, and re-entrant features) on the build angle. Innovative analysis methods are proposed to correlate shape and position of pores, to determine the angular-resolved Surface roughness, and to quantify the amount of re-entrant surface features, q. A meshing of the XCT surface enables the correlation of q with the classical Surface roughness Pa. This analysis leads to the conclusion that there is a linear correlation between q and Pa. However, it is conjectured that there must be a threshold of surface roughness, below which no re-entrant features can be build.
About the Role of Interfaces on the Fatigue Crack Propagation in Laminated Metallic Composites
(2021)
The influence of gradients in hardness and elastic properties at interfaces of dissimilar materials in laminated metallic composites (LMCs) on fatigue crack propagation is investigated experimentally for three different LMC systems: Al/Al-LMCs with dissimilar yield stress and Al/Steel-LMCs as well as Al/Ti/Steel-LMCs with dissimilar yield stress and Young’s modulus, respectively. The damage tolerant fatigue behavior in Al/Al-LMCs with an alternating layer structure is enhanced significantly compared to constituent monolithic materials. The prevalent toughening mechanisms at the interfaces are identified by microscopical methods and synchrotron X-ray computed tomography. For the soft/hard transition, crack deflection mechanisms at the vicinity of the interface are observed, whereas crack bifurcation mechanisms can be seen for the hard/soft transition. The crack propagation in Al/Steel-LMCs was studied conducting in-situ scanning electron microscope (SEM) experiments in the respective low cycle fatigue (LCF) and high cycle fatigue (HCF) regimes of the laminate. The enhanced resistance against crack propagation in the LCF regime is attributed to the prevalent stress redistribution, crack deflection, and crack bridging mechanisms. The fatigue properties of different Al/Ti/Steel-LMC systems show the potential of LMCs in terms of an appropriate selection of constituents in combination with an optimized architecture. The results are also discussed under the aspect of tailored lightweight applications subjected to cyclic loading.
Scanning Manufacturing Parameters Determining the Residual Stress State in LPBF IN718 Small Parts
(2021)
The influence of scan strategy on the residual stress (RS) state of an as-built IN718 alloy produced by means of laser powder bed fusion (LPBF) is investigated. Two scan vector rotations (90°-alternation and 67°-rotation), each produced following two different scan vector lengths (long and short), are used to manufacture four rectangular prisms. Neutron diffraction (ND) and laboratory X-ray diffraction (XRD) techniques are used to map the bulk and surface RS state, respectively. The distortion induced upon removal from the baseplate is measured via profilometry. XRD measurements show that the two long scan vector strategies lead to higher RS when compared with the equivalent short scan vector strategies. Also, the 67°-rotation strategies generate lower RS than their 90°-alternation counterparts. Due to the lack of reliable stress-free d0 references, the ND results are analyzed using von Mises stress. In general, ND results show significant RS spatial non-uniformity. A comparison between ND and distortion results indicates that the RS component parallel to the building direction (Z-axis) has a predominant role in the Z-displacement. The use of a stress balance scheme allows to discuss the d0 variability along the length of the specimens, as well as examine the absolute RS state.
This study is shown as an example of the potential of synchrotron X-ray refraction technique to determine the evolution of damage in brittle (microcracked) materials. The strength of X-ray refraction resides in its high detectability of features (e.g., cracks, pores) within large volumes, enabling a macroscopic characterization of the microstructure. The case study is a Zirconia-based cast refractory, which is aimed to function at high temperatures (even in excess of 1700°C) in industrial furnaces to enable the production of special glasses. Therefore, this material must withstand severe in-service conditions (both thermomechanical and chemical). X-ray refraction technique is used to monitor the microcracking evolution of the material, which was previously subjected to thermal cycles (crossing the martensitic phase transformation around 1000°C) at two different stress levels.
The residual stress (RS) in laser powder bed fusion (LPBF) IN718 alloy samples produced using a 67°-rotation scan strategy is investigated via laboratory X-ray diffraction (XRD) and neutron diffraction (ND). The location dependence of the strain-free (d₀) lattice spacing in ND is evaluated using a grid array of coupons extracted from the far-edge of the investigated specimen. No compositional spatial variation is observed in the grid array. The calculated RS fields show considerable non-uniformity, significant stress gradients in the region from 0.6 to 2 mm below the surface, as well as subsurface maxima that cannot be accounted for via XRD. It is concluded that failure to determine such maxima would hamper a quantitative determination of RS fields by means of the stress balance method.
The complexity of any microstructural characterization significantly increases when there is a need to evaluate the microstructural evolution as a function of temperature. To date, this characterization is primarily performed by undertaking elaborative ex-situ experiments where the material’s heating procedure is interrupted at different temperatures or times. Moreover, these studies are often limited to a region smaller than the representative elementary volume, which can lead to partial or even biased interpretations of the collected data. This limitation can be greatly overcome by using in-situ synchrotron X-ray refraction (SXRR). In this study, SXRR has been combined with in-situ heat treatment to monitor the porosity evolution as a function of temperature. It is shown that SXRR is a robust and straightforward method for time-resolved (3-5 min required per scan) evaluation of thermally induced microstructural changes over macroscopically relevant volumes.
The complexity of any microstructural characterization significantly increases when there is a need to evaluate the microstructural evolution as a function of temperature. To date, this characterization is primarily performed by undertaking elaborative ex-situ experiments where the material’s heating procedure is interrupted at different temperatures or times. Moreover, these studies are often limited to a region smaller than the representative elementary volume, which can lead to partial or even biased interpretations of the collected data. This limitation can be greatly overcome by using in-situ synchrotron X-ray refraction (SXRR). In this study, SXRR has been combined with in-situ heat treatment to monitor the porosity evolution as a function of temperature. This technique is a robust and straightforward method for time-resolved (3-5 min required per scan) evaluation of thermally induced microstructural changes over macroscopically relevant volumes.
An overview of the main Non-Destructive activities conducted at BAM for the microstructural characterization of Additive Manufacturing (AM) materials will be presented. Focus is made on the study of the influence of Selective Laser Melted (SLM) scan strategies on the defect population of a Ti-6Al-4V alloy using the Analyzer Based Imaging (ABI) technique available at the BAMline (BESSY II synchrotron facility). ABI technique takes advantage of X Ray refraction at interfaces to enable the determination of porosity features (orientation, homogeneity, etc.) within large volumes, otherwise not possible to image by means X ray micro Computed Tomography.
Additionally, for a SLM IN718 material, Energy Dispersive X Ray Diffraction (subsurface measurements at 100 µm depth) and neutrons diffraction (internal measurements at 3 mm depth) are combined with distortion measurements to produce a 3D description of the Residual Stress distribution throughout the entire sample.
As opposed to reviewing results on experimental determination of residual stress by diffraction, this paper discusses the open issues when dealing with residual stress determination in additive manufactured parts, in particular those manufactured with laser powder bed fusion techniques. Three points are addressed in detail: (a) the proper determination of the strain-free reference d0, (b) the problem of the determination of the principal axes, and (c) the use of the correct diffraction elastic constants. It is shown that all methods to determine the strain-free reference d0 suffer from caveats, and care must be taken in evaluating the most suitable for the problem being tackled. In addition, it is shown that, in some systems, the principal axes do correspond to the geometrical axes of the specimen, but this needs to be systematically checked, especially in the case of uni- or bidirectional hatching strategies. Finally, the need to experimentally determine the proper diffraction elastic constants is underlined, especially in the case of strongly textured specimens, which again depends on the deposition strategy.